1 Technical Field of the Invention
The present invention relates generally to a simple structure of an optical object detection apparatus for vehicles such as a laser radar which is designed to monitor a front and a lateral zone around the vehicle.
2 Background Art
Japanese Patent First Publication No. 7-98381 discloses a laser radar designed to measure the distance to an object such as a vehicle traveling ahead of a system vehicle equipped with the laser radar. U.S. Pat. No. 5,463,384 teaches an object detection device designed to monitor a lateral area of a vehicle.
The former system uses a semiconductor laser and consists of a pulsed light emitting circuit, a laser outputting optical system, a laser receiving optical system, a pulsed light sensitive circuit, a timer circuit, and a signal processing circuit. The timer circuit determines the amount of time required by a pulsed light outputted by the pulsed light emitting circuit through the laser outputting optical system to travel to and return from an object. The signal processing circuit works to determine the distance to the object using the amount of time calculated by the timer circuit.
The latter system uses a photocoupler made up of an LED and a photodiode or a photointerruptor and consists, like the former system, of a light emitting circuit, a light emitting optical system, a light receiving optical system, and a light sensitive circuit. The system works to sense reception of a return of a light signal from an object such as a vehicle to detect the presence of the object.
The above systems have the following problems and still left room for improvement.
Specifically, monitoring a plurality of different areas around the vehicle requires mounting a plurality of separate optical systems on different portions of a body of the vehicle, which results in undesirable increases in consumption of electrical power and manufacturing cost. An additional problem is also encountered in that portions of the body of the vehicle on which the optical systems are allowed to be mounted are limited depending upon the size of the optical systems. Further, a bulky structure of the optical systems mar the appearance of the vehicle.